SONIC FATIGUE DAMPING SYSTEM DEVELOPMENT
DOUGLAS AIRCRAFT CO INC EL SEGUNDO CALIF
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A series of commercially available polymer compositions was evaluated to obtain information on the material properties required for efficient damping coatings to extend the life of aircraft structure subject to sonic fatigue. Results of tests devised to determine dynamic properties and vibration damping behavior of these materials are discussed. Reduced test data in the form of ratios indicating stress reduction due to damping and also due to adhesion between structural elements are presented. From these ratios, combined efficiencies were determined and are used as the basis for classifying the test materials into efficiency categories for the test temperature of minus 65 degrees F. to 180 degrees F., and frequencies of 150 and 300 cycles per second. Several promising new compounds were developed, based on test results which indicated that a viscoelastic layer between two rigid surfaces produced a highly effective damping system. Author, modified-PL.